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<head><title>����</title></head>
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                <p><a href="readme.htm">����</a></p>

                <p align=center><b>������ deltat T �ļ���</b></p>

                <p>�����㷨���ԣ�����պ���ֹٷ���վ�� <a href='http://eclipse.gsfc.nasa.gov/SEcat5/deltat.html'
                                                  target='_blank'>��ǧ����ʳ����[Espenak and Meeus]</a></p>

                <p>��ѧʱ������ʱ�Ĳ�ֵ����T = TD -
                    UT1�������������Ц�Tȡֵ�����Ļ���ͬ����Ҫ��֮ͬ������2150���Ժ���ٶ�ȡֵΪ31������ȡֵΪ32��</p>
                <center>
                    <b>��T�Ĳο�ֵ</b>
                    <table style='font-size:16px;text-align:center' width='350' border="1">
                        <tr bgcolor='#CCDDFF'>
                            <td><b>���</b></td>
                            <td><b>��T</b></td>
                            <td><b>���</b></td>
                        </tr>
                        <tr>
                            <td>-500</td>
                            <td> 17190</td>
                            <td>430</td>
                        </tr>
                        <tr>
                            <td>-400</td>
                            <td> 15530</td>
                            <td>390</td>
                        </tr>
                        <tr>
                            <td>-300</td>
                            <td> 14080</td>
                            <td>360</td>
                        </tr>
                        <tr>
                            <td>-200</td>
                            <td> 12790</td>
                            <td>330</td>
                        </tr>
                        <tr>
                            <td>-100</td>
                            <td> 11640</td>
                            <td>290</td>
                        </tr>
                        <tr>
                            <td>0</td>
                            <td> 10580</td>
                            <td>260</td>
                        </tr>
                        <tr>
                            <td>100</td>
                            <td> 9600</td>
                            <td>240</td>
                        </tr>
                        <tr>
                            <td>200</td>
                            <td> 8640</td>
                            <td>210</td>
                        </tr>
                        <tr>
                            <td>300</td>
                            <td> 7680</td>
                            <td>180</td>
                        </tr>
                        <tr>
                            <td>400</td>
                            <td> 6700</td>
                            <td>160</td>
                        </tr>
                        <tr>
                            <td>500</td>
                            <td> 5710</td>
                            <td>140</td>
                        </tr>
                        <tr>
                            <td>600</td>
                            <td> 4740</td>
                            <td>120</td>
                        </tr>
                        <tr>
                            <td>700</td>
                            <td> 3810</td>
                            <td>100</td>
                        </tr>
                        <tr>
                            <td>800</td>
                            <td> 2960</td>
                            <td>80</td>
                        </tr>
                        <tr>
                            <td>900</td>
                            <td> 2200</td>
                            <td>70</td>
                        </tr>
                        <tr>
                            <td>1000</td>
                            <td> 1570</td>
                            <td>55</td>
                        </tr>
                        <tr>
                            <td>1100</td>
                            <td> 1090</td>
                            <td>40</td>
                        </tr>
                        <tr>
                            <td>1200</td>
                            <td> 740</td>
                            <td>30</td>
                        </tr>
                        <tr>
                            <td>1300</td>
                            <td> 490</td>
                            <td>20</td>
                        </tr>
                        <tr>
                            <td>1400</td>
                            <td> 320</td>
                            <td>20</td>
                        </tr>
                        <tr>
                            <td>1500</td>
                            <td> 200</td>
                            <td>20</td>
                        </tr>
                        <tr>
                            <td>1600</td>
                            <td> 120</td>
                            <td>20</td>
                        </tr>
                        <tr>
                            <td>1700</td>
                            <td> 9</td>
                            <td>5</td>
                        </tr>
                        <tr>
                            <td>1750</td>
                            <td> 13</td>
                            <td>2</td>
                        </tr>
                        <tr>
                            <td>1800</td>
                            <td> 14</td>
                            <td>1</td>
                        </tr>
                        <tr>
                            <td>1850</td>
                            <td> 7</td>
                            <td>&lt1</td>
                        </tr>
                        <tr>
                            <td>1900</td>
                            <td> -3</td>
                            <td>&lt1</td>
                        </tr>
                        <tr>
                            <td>1950</td>
                            <td> 29</td>
                            <td>&lt0.1</td>
                        </tr>
                    </table>
                    <br>
                    <table style='font-size:16px;text-align:center' width='350' border="1">
                        <tr bgcolor='#CCDDFF'>
                            <td><b>���</b></td>
                            <td><b>��T</b></td>
                            <td><b>5��<br>�仯��</b></td>
                            <td><b>ÿ��<br>ƽ��</b></td>
                        </tr>
                        <tr>
                            <td>1955<br>1960<br>1965<br>1970<br>1975<br>1980<br>1985<br>1990<br>1995<br>2000<br>2005
                            </td>
                            <td>31.1<br>33.2<br>35.7<br>40.2<br>45.5<br>50.5<br>54.3<br>56.9<br>60.8<br>63.8<br>64.7
                            </td>
                            <td> - <br>2.1<br>2.5<br>4.5<br>5.3<br>5.0<br>3.8<br>2.6<br>3.9<br>3.0<br>0.9</td>
                            <td> - <br>0.42<br>0.50<br>0.90<br>1.06<br>1.00<br>0.76<br>0.52<br>0.78<br>0.60<br>0.18</td>
                        </tr>
                    </table>

                </center>
                <p>������ʷ��¼��ֱ�ӵ����Ĺ۲�(������ϱ��)�����Եõ�����һ��򵥶���ʽֱ�Ӽ��㦤T�����÷�Χ -1999��3000��</p>

                <p>���Ƕ��壺y = year + (month - 0.5)/12������õ������м�ʱ�̵�yֵ���ɴ˼��� ��T �Ѿ��㹻��ȷ��</p>

<pre>
<b>-500�� ��ǰ��</b>
  ��T = -20 + 32 * u^2��ʽ�� u = (y-1820)/100

<b>-500�� �� +500�꣺</b>

  ��T = 10583.6 - 1014.41 * u + 33.78311 * u^2 - 5.952053 * u^3
        - 0.1798452 * u^4 + 0.022174192 * u^5 + 0.0090316521 * u^6 
  ʽ�� u = y/100

<b>+500�� �� +1600�꣺</b>
  ��T = 1574.2 - 556.01 * u + 71.23472 * u^2 + 0.319781 * u^3
        - 0.8503463 * u^4 - 0.005050998 * u^5 + 0.0083572073 * u^6
  ʽ�� u = (y-1000)/100

<b>+1600�� �� +1700�꣺</b>
  ��T = 120 - 0.9808 * t - 0.01532 * t^2 + t^3 / 7129
  ʽ�� t = y - 1600

<b>+1700�� �� +1800�꣺</b>
  ��T = 8.83 + 0.1603 * t - 0.0059285 * t^2 + 0.00013336 * t^3 - t^4 / 1174000
  ʽ�� t = y - 1700

<b>+1800 �� +1860��</b>
	��T = 13.72 - 0.332447 * t + 0.0068612 * t^2 + 0.0041116 * t^3 - 0.00037436 * t^4 
		+ 0.0000121272 * t^5 - 0.0000001699 * t^6 + 0.000000000875 * t^7
	where: t = y - 1800

<b>1860 �� 1900��</b>
  ��T = 7.62 + 0.5737 * t - 0.251754 * t^2 + 0.01680668 * t^3
        -0.0004473624 * t^4 + t^5 / 233174
  ʽ�� t = y - 1860

<b>1900 �� 1920��</b>

	��T = -2.79 + 1.494119 * t - 0.0598939 * t^2 + 0.0061966 * t^3 - 0.000197 * t^4
	where: t = y - 1900

<b>1920 �� 1941��</b>
  ��T = 21.20 + 0.84493*t - 0.076100 * t^2 + 0.0020936 * t^3
  ʽ�� t = y - 1920

<b>1941 �� 1961��</b>
  ��T = 29.07 + 0.407*t - t^2/233 + t^3 / 2547
  ʽ�� t = y - 1950

<b>1961 and 1986, calculate:</b>
  ��T = 45.45 + 1.067*t - t^2/260 - t^3 / 718
  ʽ��t = y - 1975

<b>1986 �� 2005��</b>
  ��T = 63.86 + 0.3345 * t - 0.060374 * t^2 + 0.0017275 * t^3 + 0.000651814 * t^4 
       + 0.00002373599 * t^5
  ʽ�� t = y - 2000

<b>2005 �� 2050��</b>
  ��T = 62.92 + 0.32217 * t + 0.005589 * t^2
  ʽ�� t = y - 2000
  �ñ��ʽԴ�ڶ�2010��2050�ꦤT������ơ�
  2010(66.9��)�Ǵ�2005��ʼ��0.39��/��(1995��2005��ƽ��ֵ)���ٶ��������Ƶõ���
  2050(93��)�Ǵ�2010��ʼ��0.66��/����ٶ�(1901��2000��ƽ��ֵ)�������Ƶõ���

<b>2050 �� 2150��</b>
  ��T = -20 + 32 * ((y-1820)/100)^2 - 0.5628 * (2150 - y)
  
  ����ʽ�νӣ����2050���Ĳ�����

<b>2150�� �Ժ�</b>
  ��T = -20 + 32 * u^2
  ʽ�� u = (y-1820)/100
</pre>

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